Method and apparatus for classifying and concentrating materials



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um l wvrv i111|r| 4 United States Patent O IVIETHOD AND APPARATUS FORCLASSIFYING AND CNCENTRATING MATERIALS Thomas R. Morton, Schumacher,Ontario, Canada Application September 1, 1951, Serial No. 244,747 4Claims. (Cl. 209-144) This invention relates to the treatment of nelydivided solids for the purpose of classifying them on the basis ofweight of the particles, as well as for the purpose of extracting fromthe mass of solid particles a desired concentrate.

The so-called cyclone separators, involving the use of centrifugalforce, have been long used for the treatment of finely divided solidsand many variations have been suggested in the manner of constructingand using such separators.

The object of the present invention is to provide an improved method andapparatus, utilizing the essential operating principal of the cycloneseparator, for the selective classification aud/r concentration of thesolids present in a fluid mass of finely divided material.

It is well recognized that the effect of centrifugal force, applied to afluid mass of finely divided solids in a confined circular space, is toseparate the solid particles into heavy and lighter fractions which maybe withdrawn separately from the confined space. Normally the lightfraction is discharged at the top and the heavy fraction at the bottomof the separator. Two or more such cyclone separators have beenconnected in series in order to repeat the separating effect of thecentrifugal force.

It has now been found that greatly improved results are obtained when asubstantial portion of the heavy fraction, which appears about the sidewall of the cyclone separator, is withdrawn from the separator at aboutthe mid point between the top and bottom of the separator andtangentially fed into a second similar separator, so that the heavyfraction relatively free from lighter weight solids is resubjected tothe action of centrifugal force. To further enhance the desiredseparation of solid particles a fluid under pressure is tangentially fedinto the second separator adjacent its top to dilute the thick materialand facilitate its classification.

The withdrawal from the initial cyclone separator to the secondseparator should be substantially at the mid point between the top andbottom of the initial separator in order to utilize the improved methodof the invention to best advantage and thus obtain the maximumbeneficial capacity of the initial separator unit.

The invention will now be described with reference to the accompanyingdrawing in which Figure l is an elevation view of two separatorsconnected in series as shown.

Figure 2 is a sectional plan view of the arrangement shown in Figure 1.

Figure 3 is similar to Figure 1 with a variation of the inner contour ofthe initial separator and Figure 4 is a sectional plan view of thearrangement of Figure 3.

In the drawing 1 is a cyclone separator having a tangential feed inlet2, an overflow outlet 3 and an underflow outlet 4. As shown the confinedseparating zone is cylindrical in form, preferably with a topcylindrical section, as is commonly used. It is essential that theseparating zone be circular in cross section through its length. It maybe conical.

5 is a similar cyclone separator, preferably smaller in size, having anoverflow outlet 6, an underflow outlet 7 and a tangentially arrangedfeed inlet 8 connected as shown to separator 1 substantially half waybetween the top and bottom of the latter. A fluid inlet 9 istangentially arranged at a point remote from inlet 8 and preferably atthe opposite side of the separator 5. Within this inlet is ,i 2,701,056Patented Feb. 1, 1955 ICC a valve 10 and a pressure gauge, not shown, ispreferably located between the valve and the separator.

In the form shown in Figure 3 the wall of separator 1 is inwardlyinclined at the lower lip of the outlet 8 to change at this point thedirection of downward flow of the descending fraction of material undertreatment. The thus reduced diameter of the lower section of theseparator increases the velocity of travel of the fluid mass undertreatment.

Both separators are preferably rubber lined to avoid abrasion and undueinterference with the spiral downward flow of the heavy fractionadjacent the wall.

In accordance with the method of the invention a fluid mass of finelydivided solids is fed tangentially into the top of the initialseparating zone under pressure, say 20 to 50 p. s. i., to form an outerdescending fraction of relatively heavy material and an inner ascendingfraction of lighter material in accordance with usual practice in theuse of cyclone separators. A substantial portion of the outer heavyfraction is withdrawn as indicated and fed tangentially into the top ofthe second separating zone, while the remaining portion of the heavyouter fraction is allowed to proceed downwardly to permit increasedremoval therefrom of remaining light weight material which enters theaxially ascending inner fraction of light material to be discharged asoverflow. The heavy material is discharged as underflow.

The Withdrawn portion of the heavy fraction as it enters the secondseparating zone is diluted by incoming fluid under pressure and theadditional force imparted thereto causes it to travel circumferentiallythrough the zone for further classification or concentration on thebasis of the relative Weight of the solids particles. The separatedlight weight material is discharged upwardly as overflow and the heavyremaining material downwardly as underflow.

As illustrative of the efficiency of the invention in comparison withthat obtained by use of the normal cyclone separation, the followingexamples are given. In determining efficiencies, use is made of thestandard formula where E is efficiency of classification, f per centundersize in the feed, c percent undersize in the overflow and t percent undersize 1n the underflow.

(l) Separation of 10 micron material:

Single cyclone E=50.6% The present device E=69.2% (2) Separation of 74micron material (200 mesh):

Single cyclone .4% The present device E=76.0%

The invention improves the efficiency of classification by substantiallymore than 30%, and with little or no increase in power consumption ortime of operation. It is an easy matter to adjust operating conditionsto meet the requirements of any desired specific size of material to beseparated. The material to be processed may contain particles having adiameter of 1A inch or more and the term finely divided as used hereinis to be so interpreted.

It will be obvious to those skilled in the art that the invention may beapplied in a variety of operations using an aqueous or gaseousfluidizing medium for the finely divided particles. Examples are,concentrating the gold or other metal values in ores into smallfractions, removing fines of a specific size from the circuit of oregrinders and thus reducing the circulating load. In the latter theapparatus is inserted in series in the aqueous grinding circuit and theoverflow fraction of sufficiently fine material is removed from thecirculating load while the oversize material remains in the circuit.

It is now well recognized in the use of cyclone separators that thedimensions of the separating zone, inlets and outlets, volume of feed,feed pressure and the like are correlated. These known factors areequally app icable herein and form no part of the present invention.

I claim:

1. A method of separating solids from a fluid mass `containing solids ofvarying particle size which comprises feeding the fluid mass underpressure tangentially into a confined separating zone, circular in crosssection, to form an inner axially ascending portion of light weightmaterial and an outer descending portion of heavier material,withdrawing heavy material at approximately the mid point between thetop and bottom of the separating zone, discharging it tangentially intoa second similar separating zone adjacent the top thereof, admitting uidtangentially under pressure adajcent the top of said second zone todilute said heavy material and withdrawing light weight material axiallyat the top of each separating zone and heavier material axially at thebottom of each zone.

2. Apparatus of the character described comprising a pair of separatingchambers circular in cross section, an axially disposed discharge outletat the top and bottom of each chamber, a tangentially disposed orificesubstantially midway between the top and bottom of the first of saidchambers arranged to discharge tangentially adjacent the top of theother of said charnbers, means for admitting a uid mass containingsolids tangentially under pressure adjacent the top of the first of saidchambers and means for admitting uid tangentialla); under pressureadjacent the top of the other cham- 3. Apparatus of the characterdescribed comprising first and second separating chambers circular incross section, an axially disposed discharge outlet at the top andbottom of each chamber, a tangentially disposed orifice substantiallymidway between and in widely spaced relation to the top and bottom ofsaid tirst chambers, said orifice communicating with the top portiononly of said second chamber, and being arranged to dischargetangentially thereinto, and means for admitting a fluid mass containingsolids tangentially under pressure adjacent the top of said rst chamber.

4. Apparatus of the character described comprising first and secondseparators, an axially disposed discharge outlet at the top and bottomof each separator, a tangentially arranged connection connecting saidseparators, said separators communicating in series through saidconnection, said connection being located at approximately the mid pointbetween the bottom and top of the lirst separator and at the top portionof the second separator, a tangentially arranged feed inlet adjacent thetop of said rst separator, and a tangentially arranged uid feed pipeadjacent the top of said second separator at a point substantiallyopposite said connection.

References Cited in the tile of this patent UNITED STATES PATENTS762,866 Allen June 21, 1904 762,867 Allen June 2l, 1904 1,701,942Andrews Feb. 12, 1929 2,039,692I Van Tongeren May 5, 1936 2,180,694 ReedNov. 21, 1939 2,418,061 Weinberger Mar. 25, 1947 2,550,341 Fontein Apr.24, 1951 FOREIGN PATENTS 156,869 Germany Sept. l1, 1939 613,660 GreatBritain Dec. 1, 1948 983,180 France June 20, 1951 984,678 France July 9,1951

1. A METHOD OF SEPARATING SOLIDS FROM A FLUID MASS CONTAINING SOLIDS OFVARYING PARTICLE SIZE WHICH COMPRISES FEEDING THE FLUID MASS UNDERPRESSURE TANGENTIALLY INTO A CONFINED SEPARTING ZONE, CIRCULAR IN CROSSSECTION, TO FORM AN INNER AXIALLY ASCENDING PORTION OF LIGHT WEIGHTMATERIAL AND AN OUTER DESCENDING PORTION OF HEAVIER MATERIAL,WITHDRAWING HEAVY MATERIAL AT APPROXIMATELY THE MIND POINT BETWEEN THETOP AND BOTTOM OF THE SEPARATING ZONE, DISCHARGING IT TANGENTIALLY INTOA SECOND SIMILAR SEPARATING ZONE ADJACENT THE TOP THEREOF, ADMITTINGFLUID TANGENTIALLY UNDER PRESSURE ADJACENT THE TOP OF SAID SECOND ZONETO DILUTE SAID HEAVY MATERIAL AND WITHDRAWING LIGHT WEIGHT MATERIALAXIALLY AT THE TOP OF EACH SEPARATING ZONE AND HEAVIER MATERIAL AXIALLYAT THE BOTTOM OF EACH ZONE.
 2. APPARATUS OF THE CHARACTER DESCRIBEDCOMPRISING A PAIR OF SEPARATING CHAMBERS CIRCULAR IN CROSS SECTION, ANAXIALLY DISPOSED DISCHARGE OUTLET AT THE TOP AND BOTTOM OF EACH CHAMBER,A TANGENTIALLY DISPOSED ORIFICE SUBSTANTIALLY MIDWAY BETWEEN THE TOP ANDBOTTOM OF THE FIRST OF SAID CHAMBERS ARRANGED TO DISCHARGE TANGENTIALLYADJACENT THE TOP OF THE OTHER OF SAID CHAMBERS, MEANS FOR ADMITTING AFLUID MASS CONTAINING SOLIDS TANGENTIALLY UNDER PRESSURE ADJACENT THETOP OF THE FIRST OF SAID CHAMBERS AND MEANS FOR ADMITTING FLUIDTANGENTIALLY UNDER PRESSURE ADJACENT THE TOP OF THE OTHER CHAMBER.